Detailed yield assessment of carbon nanostructures synthesized by submerged arc discharge in water

Submerged arc discharge in water (SADW) is one of the most effective methods for the synthesis of high-quality carbon nanostructures (CNSs). Despite the numerous published studies on SADW, systematic data on yield is still lacking. The SADW runs as a succession of stable and unstable zones, but the influence of these zones on its yield has not yet been explored. The CNSs were synthesised in a SADW facility with a micro-positioning system controlled by current feedback, stabilisation via ballast resistance, and data recorded by a five-parameter correlated measurement system. The synthesis products were characterised by x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) adsorption isotherms. In this study, an approach is presented to determine the SADW yield by analysing the correlation between the process parameters recorded with the experimental setup and gravimetric measurements. In the work, the relationship between the formation of the different CNSs and the stable and unstable zones is discussed. The yield was determined at a current of 30 A, which is considered the optimal current for CNSs synthesis, and the estimation obtained indicates that it is in the range of 1%–1.3%. The energy consumption to produce CNSs was assessed to be around 80 kJ.mg−1. The results obtained contribute to clarifying some of the factors that influence yield and how to optimise it. This work provides a useful reference point for future work associated with CNS synthesis using SADW.